$(document).ready(function() {
  // 设备宽度
  var q = document.getElementById('welcomeCanvas')
  var w = document.body.clientWidth | document.documentElement.clientWidth
  var h = document.body.clientHeight | document.documentElement.clientHeight
  q.height = h - 95
  q.width = w
  var width = q.width
  var height = q.height
  var yPositions = Array(300).join(0).split('')
  var ctx = q.getContext('2d')
  var draw = function() {
    ctx.fillStyle = 'rgba(0,0,0,.05)'
    ctx.fillRect(0, 0, width, height)
    ctx.fillStyle = 'green'/* 代码颜色 */
    ctx.font = '10pt Georgia'
    yPositions.map(function(y, index) {
      var text = String.fromCharCode(1e2 + Math.random() * 330)
      var x = (index * 10) + 10
      q.getContext('2d').fillText(text, x, y)
      if (y > Math.random() * 1e4) {
        yPositions[index] = 0
      } else {
        yPositions[index] = y + 10
      }
    })
  }
  RunMatrix()
  function RunMatrix() {
    var Game_Interval = setInterval(draw, 30)
  }
})
